(no subject)
Jennifer Martin
1st Period
Dr. D
Cell Cycle
Without the ability of a cell to divide, the basis of reproduction for every organism would be nonexistent. Eukaryotic cells that divide undergo a repeating cell cycle, which contains a sequence of phases in which a cell divides to form two daughter cells.
Cell division gives a multicellular organism the ability to grow to adult size, replaces worn-out or damaged cells, and keeps the total cell number constant (in a mature cell). In the human body, the sum of sixty trillion cells is controlled by division by cells every second. The regulation of cell division varies depending on the cell-some cells divide daily, others less often, and highly specialized cells (such as mature muscle cells) do not divide at all.
Chromosomes are made of forty percent DNA and sixty percent protein, which are made of genes, which are made of nucleotides, which are made of bases (Adenine, Guanine, Cytosine and Thymine), sugar and phosphate. DNA is long, string-like and is organized by winding around protein called histones. Chromosomes are found in Eukaryotic cells. In prokaryotic cells (bacteria), naked DNA is found. A chromatid is a chromosome in a dividing cell that is thick and condensed, and a chromatin is a chromosome in a nondividing cell that is thin and string-like.
Before cell division occurs, the cell doubles all of the contents in the cytoplasm and duplicates its chromosomal DNA to get ready for division. The majority of the cell cycle takes place in the eighteen hour long interphase, when a cell’s metabolic activity is very high and the cell does most of its growing. The cell performs its various functions within the organism, duplicating chromosomes. The interphase usually lasts for at least ninety percent of the total time required for the cell cycle. The main event of the chromosomal duplication process is DNA synthesis, which occurs in the middle of interphase, serving as the foundation for dividing interphase into three further phases. The first subphase (G ) takes eight hours to complete and is the period before DNA synthesis begins in which the cell increases its supply of proteins, grows in size, and increases the numbers of many of its organelles, such as mitochondria and ribosomes. The ‘G’ in G stands for gap, despite the fact that subphase G is obviously not a resting period. After G takes place, the S phase begins DNA synthesis (or replication). This phase takes six hours to complete and starts with single chromosomes, but ends with double chromosomes that contain two sister chromatids after DNA replication has taken place. G , the third subphase of interphase, takes the cell from the completion of DNA synthesis in G to the onset of cell division. G is not only a time of metabolic activity (as are the other subphases) but synthesizes some of the most essential proteins to cell division. This phase takes four hours to complete.
Eukaryotic cell division involves mitosis and cytokinesis (which, taken together, make up the forty-five minute long mitotic phase, or M phase, of the cell cycle). It must first go through mitosis, in which the nucleus and its contents (including the double chromosomes) divide and are evenly distributed to create two daughter nuclei. Mitosis has four main stages: prophase, metaphase, anaphase, and telophase. The chromosomes depend on the mitotic spindle, a structure of microtubules that guides the separation of the two sets of daughter chromosomes. The spindle microtubules emerge from two centrosomes (microtubule-organizing centers), which are clouds of cytoplasmic material.
Usually, afterwards mitosis the Eukaryotic cell will take place in cytokinesis, in which the cytoplasm divides into two parts. The combination of mitosis and cytokinesis produces two genetically identical daughter cells (diploid cells) with the same number of chromosomes as the mother cell, each containing a single nucleus, cytoplasm and a plasma membrane. Plant cells have a cell wall and have to form a cell plate to finally separate the daughter cells. Prokaryotic cells (bacteria) divide by binary fission. They replicate their DNA and simply split into two daughter cells, without performing mitosis.
After cytokinesis has taken place and the two daughter cells are produced, each daughter cell will then begin the G stage, entering the cell cycle. This completes the cell cycle and begins the process once again.
1st Period
Dr. D
Cell Cycle
Without the ability of a cell to divide, the basis of reproduction for every organism would be nonexistent. Eukaryotic cells that divide undergo a repeating cell cycle, which contains a sequence of phases in which a cell divides to form two daughter cells.
Cell division gives a multicellular organism the ability to grow to adult size, replaces worn-out or damaged cells, and keeps the total cell number constant (in a mature cell). In the human body, the sum of sixty trillion cells is controlled by division by cells every second. The regulation of cell division varies depending on the cell-some cells divide daily, others less often, and highly specialized cells (such as mature muscle cells) do not divide at all.
Chromosomes are made of forty percent DNA and sixty percent protein, which are made of genes, which are made of nucleotides, which are made of bases (Adenine, Guanine, Cytosine and Thymine), sugar and phosphate. DNA is long, string-like and is organized by winding around protein called histones. Chromosomes are found in Eukaryotic cells. In prokaryotic cells (bacteria), naked DNA is found. A chromatid is a chromosome in a dividing cell that is thick and condensed, and a chromatin is a chromosome in a nondividing cell that is thin and string-like.
Before cell division occurs, the cell doubles all of the contents in the cytoplasm and duplicates its chromosomal DNA to get ready for division. The majority of the cell cycle takes place in the eighteen hour long interphase, when a cell’s metabolic activity is very high and the cell does most of its growing. The cell performs its various functions within the organism, duplicating chromosomes. The interphase usually lasts for at least ninety percent of the total time required for the cell cycle. The main event of the chromosomal duplication process is DNA synthesis, which occurs in the middle of interphase, serving as the foundation for dividing interphase into three further phases. The first subphase (G ) takes eight hours to complete and is the period before DNA synthesis begins in which the cell increases its supply of proteins, grows in size, and increases the numbers of many of its organelles, such as mitochondria and ribosomes. The ‘G’ in G stands for gap, despite the fact that subphase G is obviously not a resting period. After G takes place, the S phase begins DNA synthesis (or replication). This phase takes six hours to complete and starts with single chromosomes, but ends with double chromosomes that contain two sister chromatids after DNA replication has taken place. G , the third subphase of interphase, takes the cell from the completion of DNA synthesis in G to the onset of cell division. G is not only a time of metabolic activity (as are the other subphases) but synthesizes some of the most essential proteins to cell division. This phase takes four hours to complete.
Eukaryotic cell division involves mitosis and cytokinesis (which, taken together, make up the forty-five minute long mitotic phase, or M phase, of the cell cycle). It must first go through mitosis, in which the nucleus and its contents (including the double chromosomes) divide and are evenly distributed to create two daughter nuclei. Mitosis has four main stages: prophase, metaphase, anaphase, and telophase. The chromosomes depend on the mitotic spindle, a structure of microtubules that guides the separation of the two sets of daughter chromosomes. The spindle microtubules emerge from two centrosomes (microtubule-organizing centers), which are clouds of cytoplasmic material.
Usually, afterwards mitosis the Eukaryotic cell will take place in cytokinesis, in which the cytoplasm divides into two parts. The combination of mitosis and cytokinesis produces two genetically identical daughter cells (diploid cells) with the same number of chromosomes as the mother cell, each containing a single nucleus, cytoplasm and a plasma membrane. Plant cells have a cell wall and have to form a cell plate to finally separate the daughter cells. Prokaryotic cells (bacteria) divide by binary fission. They replicate their DNA and simply split into two daughter cells, without performing mitosis.
After cytokinesis has taken place and the two daughter cells are produced, each daughter cell will then begin the G stage, entering the cell cycle. This completes the cell cycle and begins the process once again.